Process for producing synthetic lumber that is not attacked by molds



Patented Feb. 13, 1934 UNITED STATES PATENT OFFICE PROCESS FOR PRODUCINGSYNTHETIC LUMBER THAT IS NOT ATTACKED BY MOLDS No Drawing. Originalapplication June 27, 1929,

Serial No. 374,274. Divided and this application April 16, 1931. SerialNo. 530,736

3 Claims. (01. 92-40) This invention relates to the process or method oftreating synthetic lumber, paper or the like against attacks from molds.For purposes of illustration I will specifically consider and herein 5discuss the treating of synthetic lumber made from cornstalks againstsuch attacks by molds and the like. To this end the invention mayconsist of: first, cooking the unshredded corn plant under pressure;second, allowing it to stand for a certain length of time withoutwashing it; third, passing it through a rod mill or like; fourth,suitably washing the same; fifth, passing the washed product through arefining machine; sixth, treating said material with a suitable amountof water; seventh, adding to said mass 2. sizing material such as rosinor alum; eighth, forming it into a board; ninth, drying it on a suitablemachine; and tenth, spraying the formed board with a copper sulphatesolution. When such a board is formed it will be economical inmanufacture, durable and strong in use, and will be free from thepossibility of its deterioration by molds. The step by step proceduremay be varied as will hereinafter be explained.

Heretofore, a great deal of experimenting has been done in attempting tomake suitable synthetic lumber from cornstalks and from this standpointI might state that my UnitedStates Letters Patent on a Process relatingto the production of synthetic lumber from cornstalks, Patent No.1,803,737, under date of May 5, 1931, and of which this invention is adivision, goes into great detail to explain.

Suffice it to say that the examination of the cornstalk shows that it iscomposed of a hard outer shall called the cortex. This cortex surroundsa soft pulpy material known as pith or parenchyma, and this pithsurrounds elongated cell fibers called vascular bundles. Any processingof this material is difficult because of the different physicalproperties. For example, if the grinding machinery is not especiallyadapted to the purpose, the pith will be beat to a jelly long beforepieces of the outside fibers are reduced to a suitable pulp.

This causes the mat forming machine to become clogged and produce anunsatisfactory product. Likewise in the digesting of the cornstalks withchemicals, no wholly satisfactory process has been worked out becausethe pith and vascular bundles are completely hydrolyzed anddisintegrated before the cortex is properly cooked.

In the standard practice it is the custom to shred or otherwisecomminute the cornstalks before subjecting them to cooking or chemicaltreatment.

I have found that if the cornstalks be unshredded and then fed into thedigester as they come in bales or directly from the field, before theyhave been given any serious mutilation, and that if the digestion becarried out using approximately pure water, or in other words waterwhose pH value does not vary greatly from 7.0, and that if these wholeunmutilated stalks are subjected to a pressure of from thirty to onehundred pounds in contact with hot water, that there results a productwhich when properly macerated gives a board of great strength and ofhighly desirable properties for use in the parts.

I have also found that it is advisable after cooking the cornstalks forfrom one to three hours under such a pressure with hot water, that thefibers will be made tougher and that the pith cells will draw into fiberbetter and be removed more completely from the fibrous cortex cells if Iallow the cooked stalks to stand for from four to twenty-four hoursbefore they are further handled in the processes. This standing has adouble advantage in that it allows the fibers to absorb from the cookliquors ligneous or pentosic materials which probably partly oxidize andat the same time the greater amount of the cooking liquors drain awaythus reducing the necessity for excessive washing of the material.

In order to get the best results from the water digested fibers orcornstalks as prepared in the foregoing manner, I next pass thecornstalks through a heavy rod mill. This rod mill is of the usualconstruction consisting of a large drum mounted for rotation and havinga plurality of heavy rods therein.

As the drum revolves on its axis the rods naturally either tumble overeach other or rise upon the side of the drum and slide downcontinuously. It is obvious that if the rods tumble from the top portionof the drum downwardly, a pounding action will result, whereas if therods slide down the side they will give a rubbing action to the materialinside the drum.

For my purposes I prefer the rubbingaction as it draws the pith cellsinto long fibers which do not jell up and which work better whencommingled with the tough, strong cortex fibers. The obtaining of thisresult will vary with the 105 different types of rod mills, but anyskilled workman can easily determine the speed the drum should rotatefor realizing this rubbing action. Results will also depend on the ratethe cornstalks are fed into the mill. Obviously the larger 110 the rodsand rod mill the greater the feed must be in order to producesatisfactory fiber.

I have found that it is best to run the comstalks through at such a rateas to cause the cortex fibers at the discharge end to vary in lengthsfrom very short fibers to fibers of about one-half inch in length. Bestresults are not generally obtained by attempting to completely reducethe pulp in the rod mill. By passing the cornstalks through at a rate togive fibers of the above-mentioned dimensions, the pith is notexcessively jelled, but is drawn into fibers. There will also beproduced a small percentage of thread-like fibers several inches inlength which is very desirable.

It is necessary to feed into the rod mill at the same time that thestalks are going through, an amount of water such as to make thecornstalk fiber come from the discharge freely. The amount of this waterwill be at least five hundred per cent of the weight of the cornstalksfed into the mill.

After the pulp has come through the mill it is now coarse enough to befree on a screen which is so positioned as to receive the pulp. It isupon this screen that the cornstalk pulp is washed with water to removea certain amount of the pentosans and lignins produced during the watercooking. This washing must not be too thorough because the adhesiveproperties of these before-mentioned materials are desirable. If,however, none of the lignins or pentosans are washed out, the board willnot be free enough on the machines used to make up the same. The screenshould be of approximately forty mesh and may be either of the inclinedsheet type or the rotating cylinder type. As the pulp travels down andacross the screen it is washed by the water sprayed on it which can becontrolled by a valve in the water line.

If a very refined board is desired, the pulp from the washing screenshould be passed through a refiner in order to take out the small piecesof material which are sometimes termed shiners or chives. After the pulpis washed, a suitable amount of water is added to the same and to thismass usually is added a sizing material such as rosin or alum. The massis then conveyed to the board forming machine as is well known in theart.

The above discussion will give a general idea of one way of making andforming a synthetic lumber and will form a basis upon which I maydiscuss the treating of the same against molds. Therefore, generally Iwould state that this invention consists of spraying a substance ontothe board that eliminates molds.

When the pulp is placed on the board forming machine it is pressed inthe usual manner by rollers or the like and the water removed from thesame. The water thus removed is generally called white waters and I havefound that for economy of water consumption it is desirable to use thiswater by returning it to the process. I use it direct for washing thepulp and for diluting the pulp in the refining machine.

After the board mat is formed it is then pressed and dried in the usualmanner by suitable pressing and drying machinery which delivers theformed board in a hot condition. It is at this point that I spray asolution of copper sulphate, which is an excellent poison forsuccessfully combating molds onto the heated boards, which due to theirbelow normal dryness will readily absorb the solution of coppersulphate, thereby making the board mold-proof. The copper sulphate willmore fully impregnate the boards if they are stacked one on top of theother and allowed to stand in such condition for a certain length oftime.

Another method of treating the board is to spray the copper sulphate onthe board mass before it reaches the pressing and drying machinery.However, in either case the board will be successfully treated againstmolds.

I claim as my invention:

1. The process of manufacturing and producing a synthetic lumber fromcornstalks consisting of the breaking up of the cornstalks intocomparatively fine pieces, commingling the pieces with water, formingthe mass into lumber by pressing and heat drying, and lastly sprayingsaid lumber with a solution of copper sulphate, while said lumber isstill warm from said heat drying.

2. The process of manufacturing and producing a synthetic lumber fromcornstalks consisting of the cooking of the cornstalks in water underpressure, discharging the material from the cooker, breaking thematerial into particles by a suitable machine, adding liquid to theparticles, forming the mass into lumber by pressing and heat drying, andlast spraying said lumber with a copper sulphate solution, while saidlumber is still warm from said heat drying.

3. The process of manufacturing and produc ing synthetic items fromcornstalks consisting in the cooking of the unshredded corn plant inwater under pressure, discharging the material from the cooker, rubbingand breaking the cornstalks into elongated particles by a suitablemachine, treating the particles with water, forming the mass into itemsby pressing and heat drying, and last spraying said items with a coppersulphate solution, while said lumber is still warm from said heatdrying.

ORLAND R. SWEENEY.

